The present invention relates to a PIN diode switching system; in particular, incorporated in the transmission stage of a mobile radio telephone or in the form of a changeover switch for switching the antenna between transmission and reception.
In the radio-frequency band, PIN diodes are used as a controllable resistance for attenuation purposes, and as low-loss switches. PIN diodes are used in the radio-frequency field owing to the small diode dimensions, the low insertion inductance and the low blocking capacity.
As is known, when PIN-diodes which have to switch high radio-frequency power levels (RF switches) are in the reverse-biased state, they must be biased with a negative reverse voltage whose magnitude is at least as great as that of the radio-frequency voltage (peak voltage) to be switched, in order to avoid signal distortion, harmonic formation and radio-frequency attenuation. For example, a 14 V biased voltage is required in order to switch 2 watts of RF power in a mobile radio telephone with a 3.6 V supply voltage.
Until now, conventional DC voltage converters such as switched-mode converters or charge pumps (switched capacitors) have been used to produce the necessary negative reverse voltage.
The production of the relatively high negative voltage using the DC voltage converter, especially for battery-powered appliances, is associated with a high level of complexity and with high costs, while the auxiliary power which is supplied to the DC voltage converter furthermore reduces the operating time of a battery-powered appliance.
Furthermore, the voltage converter in a circuit arrangement occupies a considerable amount of space in comparison to the dimensions of present-day electronic appliances and, in particular, mobile radio telephones, which runs counter to the trend and the economic necessity to construct more convenient mobile radio telephones of smaller size.
An object of the present invention is, thus, to develop a novel and effective circuit arrangement of this generic type, which can be produced cost-effectively and without major effort.